Gear-grinding machine



A. T. BROWN.

GEAR GRINDING MACHINE. APPLICATION FILED FEB- l3. I914- RENgWED JULY 15. 1920. I

1 3,552,872, PatentedSept. 14,1920.

M SHEETS-SHEET 1.

WITNESSES.- v L I z L @M A. T. BROWN.

GEAR GRINDING MACHINE. APPLICATION FILED FEB. 13, ISM. RENEWED .IlILY L'h I9 20- Patented Sept. 14, 1920.-

I4 SNEETS-SNEET 2- l a I I i A 1 ,w. \W a l 7 a M v WITNESSES:

- A. T. BROWN. v GEAR GRINDING MACHINE. FILED FEB. 1 3, l9l4- RENEWED I I APPLICATION ULY 15, I920. 1,352,872. PatentedSept. 14,1920.

I HSHEETS SHEET 4.- v

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WIZNESSEES' A. T. BROWN GEAR GRINDING MACHINE.

APPLICATION FILED ma. 13. 1914. gsnswzo JULY 15. 1920.

1,352,872, PgtentedSept. 14, 1920.

I4 SHEETS-SHEET 5.

WITNESSES.-

' NTOR.

A TTORNEYS.

A. T. BROWN. GEAR GRINDING MACHINE. APPLICATION FILED FEB. 13, 191 RENEWED JULY 15' 1920- P s L z -T INVI- Nm 9 4 4 a m 1 o 8 I 9 x 8 m w! Z 54 5 I1, 6

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WITNESSES.-

A. T. BROWN.

I GEAR GRINDING MACHINE. APPLICATION FILED FEB. 1a. 1914. RENEWED JULY 15. 1920.

1,352,872, PawntedSept. 14, 1920.

I4 SHEETS-SHEET 7.

WITNESSES: I Ira/E2:

ATTORNEYS A. T. BROWN.

GEAR GRINDING MACHINE. APPLICATION FILED FEB. l3, l9|4--RENEWED JULY 15, 1920- PatentedSeptNM, 1920.

14 SHEETSSHEET 3;

INVEIVZQB WITNESSES:

v me/m5 A. T. BROWN. GEAR GRINDING MACHINE- APPLICATION FILED FEB. 13. I914- RENEWED JULY 15, 1920.

1,352,872; I PatentedSept. 14,1920.

-14 SHEETS-SHEET 9.

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WITNESSES: TOR.

A TTORNE Y5,

A. T. BROWN GEAR ekmome MACHINE.

' APPLICATIONv FILED FEB. 13, I914- RENEWED JULY .15, 1920.. 1,352,872, PatentedSept. 14, 1920.

14 SHE ETSSHEET IQ- I-VITZVESSES: 4 TOR.

I .4 TTORNE VS.

A. BROWN. GEAR GRINDING MACHINE.

APPLICATION FILED FEB. 13, I914- RENEWED JULY I5, I920. 1,352,872.

PatentedSept. 14, 1920.

7 J. I 1% w NT OR Y WITNESSES:

ATTORNEYS.

A. T. BROWN.

GEAR GRINDING MACHINE.

APPLICATION FILED FEB. I3, I9I4. RENEWED JULY I5, 1920.

l4 SHEETS-SHEET 12.

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A. T. BROWN.

GEAR GRINDIING MACHINE. APPLICATION E1EE0 FEB. 13, 1914. RENEWED JULY15. 1920.

Patented Sept. 14,1920.

1 1 1min] N TOR. I W Q TORNE Y8.

WI TNESSES A. T. BROWN.

GEAR GRINDING MACHINE.

APPLICATION FILED FEB. 13. 1914. RENEWED JULY 15. 1920.

1,352,872, PatentedSept. 14,1920."

I4 SHEETS-SHEET I4- lV/T/YESSES: Z; ENTOR.

ALEXANDER "r. BRowmoF SYRACUSE, NEW YORK, ASSIGNOR TO THE BROWN-LIFE UNITED sTAT sflP rENT OFFICE.

GEAR COMPANY, OF SYRACUSE, NEW YORK, A CORPORATION OF NEW YORK. I

GEAR-GRINDING MACHINE.

Specification of Letters Patent. P t t t 1 Application filed February 13, 1914, Serial No. 8 .473- Renew ed July 15, 1920. Serial 110,396,613.

To all whom it may concern Be it known that I, ALEXANDER T. BRowrI, a citizen of the United States, and a resldent of Syracuse, in the county of Onondaga and State of New York, have invented a certain new and useful Gear-Grinding .Machine, of which the following is a specigenerally, a 'movable grlnder, a gear carfication.

7 This invention has for its object the production of a machine for' grinding the teeth of gears, which is particularly simple in construction and highly eflicient, rapid and accurate in operation; and .it consists in the combinations and constructions hereinafter set forth and claimed. I

In describing this invention, referenceis had to the accompanying drawings, in

which like characters designate corresponding parts in all the views.

Figure 1 is a side elevat1on-of a machine embodying my invention. v a

- Fig. 2 is a top plan, partly broken away and partly in section, and parts being re-. moved.

Fig. 3 .is a plan view of the bed of the machine, the bearing for one of the grinders being also shown. i

Fig. 4 is an enlarged fragmentary view illustrating the operation of the, grinders on a gear.'

Fig. 5 is an enlarged front-elevation of a portion of the machine.

Fig. 6 is a sectional view on line AA, Fi 5.

ig. 7 is an enlarged front elevation of the rolling of the gear moves the gear clear of the gr1nder, an d means is provided for ro-' ear carriage, showing the means or gage for determining the initial position of the gear to be ground. I I Fig. 8 is a section on line BB,F1g. 7 Fig. 9 is an enlarged detail view illustratin the means for rolling the gear.

Fig. 10 is a front elevation. of parts seen in Fig. 9.

Fig. 11 is a fragmentary plan new of a portion of the means for rotating the gear' to bring new teeth thereof into grinding position.

Fig. 12 is an enlarged sectional view, partly in elevation, on line C-C, 'Fig'. 2.

Fig. 13 is a section on line DD, Fig. 12.

Fig. 14 is a plan View of the trimmer for the grinders. I

Fig. 15 is an inverted plan of the carriage for the cutting tools of the trimmer.

Fig. 16 is a sectional view online EE, Fig. 15.

Fig.17 is a fragmentary end elevation of the gear carriage showing the trimmer in its position assumed when trimming the grinders.

This gear grinding machine comprises,

riage arranged to hold the gear with the working face of a tooth thereof engaged with the grinder, and means for effecting a rolling movement of the gear and grinder simulating the'action of intermeshing gear teeth during the grinding operation.

In the illustrated embodiment of my invention, two grinders are used,-which are in the form of wheels having peripheral strips of abrading material engaging side faces of 2 with minimum friction with a companion gear similarly ground, it being understood that the side faces of the grinders are trimmed to the tooth it is desired to produce.

As but two teeth of the gear are engaged with the grinders, the rolling is slight.

The movement of the carriage and the tating the gear relatively to the. rolling means to bring new teeth into position to engage, or mesh with, the grinders, and the subsequent movement of the carriage and the rollingmovement of the gear brings the new teeth into and out of engagement with the grinders. v

1 is the base of the machine, and 2 designates the grinders, the grinders being here shown as wheels mounted on axles 3 journaled in bearings 4 supported on the basel of the machine, the grinders being arranged with their axes in a horizontal plane and at right angles to the plane of their respective grinding surfaces. The grinders are here shownas arrangedwith thelr axes mcllned relatively to each other so that portions of their peripheries converge and run close to ether. g

he grinders 2 are here shown as enlarged dished disks, which form the body portions thereof, and segments 5 of grinding or abrading material mounted on the edges of the disks and detachably secured in position to side faces of the disks by segmental clamping plates 6, Figs. 4 and 6, which are held in position by screws 7 extending transversely through the plates 6 and through the body portion or disks.

The abrading segments 5 project beyond the peripheral edge of the disks, and the segments of the grinders are separated at the point the grinders run closest together, such distance as to enter into the spaces on opposite sides of a single tooth of the gear being ground, the segments being arranged to engage their outer side faces simultaneously with the dissimilar or the front and rear working faces of alternate teeth of-the gear 1 The bearings 4 are in upper and lower sections, the upper section 8 being clamped to the lower section, as by cap screws 9, and suitable bushings 10, 11 surround the axles 3 within the bearings 4. Each bushing 10 has a collar 10 threading thereon and located in an annular channel in the sections 'of the bearings 4. These collars 1O take the thrust of the axles. Each bushing 10 abuts at one end againsta shoulder 10 on the axle and grinder, and nuts 3 screw on the axle against the otherend of the bushing 10. By loosening the nuts 3 and turning the collar 10, an axial adjustmentof the grinder is effected. Pulleys 12 are mounted on the outer ends-of the axles by means .of which power is applied to the grinders 2. The bearings 4 are adjusted in an arc in order to change the angle of inclination of the axes of the grinders 2 to adjust the position of the grinders to grind teeth of different pressure angles; and, as here shown, the base is formed with are shaped tongues 13 Fig.3 which fit into complemental grooves in the lower sections of 7 the bearings 4, and the lower sections of the ers 2 are inclosed by a suitable casing 17.

bearings 4 are secured to the"base by cap screws 14- adapted to enter any one of the plurality of pairs of holes 15,16. The grindmounted on the base The gear 18 is supported with its axis at an angle to the plane containing the axes ofthe wheels or grinders 2, andas the axes of the grinders are in a horizontal plane,

and as the gear 18 is a spur gear, said gear 18 is supported with its axis at a right angle to the horizontalplane containing the axes of the grinders 2. i

In this embodiment of my invention, the rolling operation simulating the intermeshing of a gear with a rack is effected by "moving the gear transversely of the grinders in a horizontal direction and rolling the gear during travel of the carriage, the turning of the gear being determined by the'moveinent of the carriage, that is, the carriage is the prime mover in actuating the gear about its formed with a way 23, Fig. 6, formed with an undercut face and movable along a complemental projecting guide 24 on the carriage 20. The ways 22, 23 are arranged above the gear out of the path ofthe dust made during the grinding operation. The spindle 21 rests at its lower end on a step or center 25 carried byra. yoke or horizontal bracket 26, Fig. 5, having an upwardly extending arm 27 moving in a tubular guide 28 supported by the carriage 19.- The bracket 26 also has an eye 29 at its free end which receives a rod 30 depending from, and fixed in, a tubular guide 31 carried by the carriage 19. The upwardly extending arm 27, which is located in the guide 28, is formed with a rack 32 with which meshes a pinion 33 mounted on a spindle 34 journaled in the bearing 35 carried by the tubular guide 28, the shaft 34 being squared at one end for receiving a suitable tool by means of which the bracket can be raised and lowered. The guide 28 is split at its lower end and is clamped on the rod 27 by clamping member 36. The eye 29 is clamped in position on the rod 30 in any suitable manner,

.as by a clamping screw 37.

The spindle 21, Fig. 6, upon which the gear is mounted, is carried in a suitable holder 38 which is journaled in a vertical bearing 39 in the carriage-19 and which extends at its upper end 40'above the bearing 39, the'holder 38 being formed conical at 38 centered. The holder 38 is held from vertical displacement by means of nuts 44, 45, one ofwhich bears against the upper face of one of the rings of the bearing 43. The spindie 21 is clamped in the holder by means of a split socket 46 which receives the upper .end of the spindle 21, the socket having an outer conical surface 47 fitting a complemental surface on the inside of the holder and the socket 46 is pulled upwardly to clamp the same on the spindle by means of a rod 48 extending lengthwise of the holder 38 within the same and fixed at its lower end to the socket and having at its upper end a threaded nut or wheel 49' screwing on the upper end thereof against the end face of the holder 38.

- Obviously, the turning of the nut 49 to pull the rod 48 upwardly, will cause the socket 46 to be clamped on the spindle 21 and movement of the nut in the opposite direction will permit the socket 46 to move outwardly and release the mandrel 21. The gear is clamped on the man rel by a nut 21.

Portions of the means for rolling the gear during the movement of the carriage, and for feeding the gear relatively to the rolling means, are mounted on the upper end 40 of the holder 38 above the carriage 19.

The means for reciprocatin the carriage 19 is here, shown as a shaft 50, igs. 1, 2 and 5, extending forwardly and rearwardly of the machine at one side thereof and having a disk 51 at its front end on which is mounted an eccentric pin 52, the motion of the shaft being transmitted to the carriage 19 through a connecting rod 53 pivoted at one end on the pin 52 and at its other end at 54 to the carriage 19. The bearing for the front end of theshaft 50 is carried by the bracket 20 on the frame or carriage 20, and the bearing for the rear of the shaft 50 is carried at the upper end of the standard 55 mounted on the base 1, the standard 55. also having a bearing for a shaft 56 having a worm gear 57, Figs. 12 and 13 thereon meshing with the worm 58 on the shaft 50. The

shaft 56 is also provided with a pulley 59 at its outer end by means of which power can ,be applied to the shaft 50.

The worm gear 58 is held from endwise movement inany suitable manner in its bearing, Fig. 12, and the shaft 50 is slidahle endwise therein in order to permit of the forward and rearward adjustment of the carriage 20, as will be presently described. As seen in Figs. 12 and 13, the shaft 50 is formed with a lengthwise keyway 50, and the gear 58 is provided with a key or pawl 58 pivoted thereto and having its 'free end taking into the keyway. The pawl is arranged to clutch the shaft 50 and gear 58 together when the gear is turning in its nor-.

, mal direction, and to permit the shaft to be turned relatively to the gear when the carriage is being reciprocated'by hand, aswhen it is being positioned to place a new gear in proper relation to the grinders.

The means for rolling the 'gear comprises a rocking part mounted concentric with the gear 18, that is, mounted on the holder 38, and means coacting with said part during movement of the carriage to rock said part,

and hence rock or roll the gear 18, said means coacting with the rocking part at a point removed from. the center thereof a distance equal to the pitch circle of the gear being ground.

As here shown, the means for causing the gear to have a rolling action during the travel of the carriage 19 comprises a roller 60, Figs. 1, 2, 5, 6, 9 and 10 mounted on the upper end 40 of the gear spindle holder 38, and normally connected thereto to rock the spindle 38, as will'be hereinafter, described, the roller being preferably of substantially the same radius as the pitch circle of the gear, and means engaging the periphery of the roller to cause the same to roll during the travel of the carriage 19, said means extending parallel to the path of the carriage 14. This means includes pairs of straps 61, 62 fixed at corresponding ends to brackets 63, 64 provided on the carriage 20, these straps 61 extending in opposite directions around the periphery of the roller and being here shown as secured thereto by rivets 65. The straps may, however, be continuous but the straps are secured to the roller, as the roller here shown is segmental, for the reason that it'is necessary that the roller make I only a small part of a'revolution.

The straps are secured to the bracket 64 by suitable couplings 66, each coupling having a threaded portion extending through oneor the other of the brackets 63, 64, and a nut 67-screwing thereon against the bracket. Each coupling also includes an equalizing lever- 68 to the opposite ends of which the straps are pivoted.

The brackets 63, 64 are adj ustably secured to the carriage 20, as seen in Fig. 1, and are clamped in position by cap screws 69 extend ing through slots 70 in said brackets and into the frame or carriage 20, this adjust. ment being for the purpose of arranging the straps substantially tangent to the rollerl'il) whenldiflferent' sizes of rollers are used, it being understood that different rollers are is preferably always of substantially the same radius as the pitch circle of the gear to be ground.

As best seen in Fig. 11, the means for feeding or shifting the gear 18 to bring'new teeth thereof into grinding position, is here shown as a ratchet wheel 71 mounted concentric withthe gear spindle holder 38 and normally fixed thereto to rotate the same (as will be hereinafter described), a shifting pawl 7 2 carried by a rocking support 73 and movable about the axis of the spindle 38, and 'means for actuating the support 73. Said-means includes a rod 74, Fig. 5, connected to the rocking lever 75 supported by the bracket 20 and'pivoted between its ends thereto, the lever 7 5 coacting witha cam 77, Fig.1, on the shaft 50. The lever 75 is shiftable along its pivot and also is adjust-' ably connected at 78 to the rod .74 in order to adjust therod endwise' and regulate the throw of the pawl 72 to difierent ratchet Wheels, as a ratchet wheel having the same numbenof teeth as the gear being ground is .provided. These ratchet wheels are the same diameter, but the number of teeth thereof correspond to the number of teeth on the gear being ground. The ratchet 7 wheel 71 is fixed to a carrier in the form of a disk 79 .having a hub 80 formed with a conical bore, which snugly fits a taper on the upper end portion of the holder 38, %he disk being held in position by a nut 81, ig. 6.

The holder 38 for the gear spindle 21, the roller 60 and ratchet wheel 71 are normally held to act as a unit during the grinding operation by means here shown as a disk 82 carried on the disk 79 beneath the ratchet wheel 71 and having a peripheral rack 83, and a lock 84 movable with the roller 60 and coacting with the rack 83. The lock 84, Fig. 11, is pivoted at 85 between its ends to a rock arm 86 movable with the roller 60,

the lock 84 having its tail 87 arranged to engage a fixed shoulder 88 provided on the frame or carriage 20 in position to, engage the tail 87 as the carriage 19 approaches the limit of each reciprocation. This movement of the lock moves the tooth 89 thereof out of engagement with the rack 83 permitting the ratchet wheel 71 to be fedby thepawl 72', the actuating cam 77 for the rod 74 and pawl 72 being timed to push the rod 74 forwardly to feed the ratchet wheel 71 just after the tail 87 of the lock 84 engages the fixed shoulder 88. The pawl carrier 73jis mounted on the hub 80 of the disk 79, and

v the rock arm 86 is provided. with a hub 89 loosely mounted on the spindle holder 38' within the roller 60, the hub being keyed to the roller, Fig. 6.

The carriage20 is shifted forwardly and rearwardly to 'adjust the machine to"difl::er ent size gears by means of the screw 91,

. Fig. 6, turning in a suitable threaded openthe particular gear to be ing in the base 1, the screw being held from endwise movement relatively to the carriage in any suitable manner and having its outerend squared at 92' for receiving a suitable tool. A micrometer adjustment 9,3 is provided on the screw for determining the amount of adjustment of the carriage for.

ound. The carriage is slidable along-su tableways 94 on thebasel.

As best seen in Figs. 7 and 8, the machine is provided with means for determining the position of gears on the carriage 19 and the spindle 21 after the proper position of the firstgear has been determined. Said means comprises a stop for limiting the carriage in a predetermined position preferably its central position, that is, its position occupied when both grinders are engaged equally or to the same extent with two teeth of the gear, and a gage or aliner adjustable to intermesh teeth thereof with teeth of the gear.

96 is the stop pivoted at 97 to a bracket 98 projecting from the carriage 20', the stop being movable on its pivot into and out of the path of" the carriage 19. 99 is the gage or aliner including a bracket 100 pivoted at 101 to the carriage 20 and carrying a rack 102, the teeth of which are of the same pressure angle as the teeth of the gear, that-is, the teeth of the rack mesh accurately with those of the gear, the rack being adjustable relativelylto the pivot 101 to be brought into position to meshwith the first gear of a batch. As. hereshown, the rack slides in a way 103 formed in the bracket 100 and is held in its adjusted position by clamping screws 104.

In operation, the first gear of a batch is placed on the spindle 21 and the carriage 19 reciprocated by hand by turning the shaft The aliner is then swung'so that the rack will engage theopposite side of the gear to that engaged by the grinders and the rack adjusted to properly mesh with said gear.

Each subsequent gear, after the osition of the carriage 19 has been determ ned by the stop 96, is turned until the rack 102, the position of which has been determined from the first gear, meshes with the subsequent ear. g To be theoretically accurate, the rack in order to coact accurately with gears of dif-- ferent sizes should move about an axis at.

a right angle to the axis of the gea'r,'s0 that the rack moves in substantially the plane of the gear, but in practice the gage pivoted as shown is accurate.

This machine is also preferably provided with means for trimming the outer sides and peripheries of the abra'ding segments 5- of the grinders to grind the faces of the teeth of the gear of the desired curvature and pressure angle, and to trim 'ofl the-peripheries of the segments so that the grinders will extend the proper distance between the teeth. This trimming means includes a frame 106, Figs. 14 to 17 ,pivoted at 107 see Fig. 5, to

. the carriage '20 at one side thereof, a carriage. 108 supported by the frame 106 and trimmers or cutterssupported by the car- -riage 108. The frame 106-is movable on its pivot into and out of position to bring the trimmers or cutting tools into operative relation to the grinders, and is held in its operative position by a clamping screw 109 which turns into a-threaded opening in the carriage 20, Fig. 14. The carriage 108 slides in suitable ways on the frame 106 and is moved to its adjusted position by means of a screw 110 threading into the frame 106 provided for moving the supports on theirpivots to wipe the points across the side faces of the abraders. Each support is here shown as T shape in general form and the pivots thereof are located at opposite ends of the head of the T and the point 113 is carried near the lower end of the le of the and extends laterally therefrom. y moving these supports about their pivots 115, the points 113 are moved back and forth over the outer side faces of the segments 5 trimming the surfaces thereof flat to a determined depth and pressure angle.

The point 116 for trimming the peripheries of the segments 5 is carried by a rock arm 117 mounted on a spindle 118 journaled in the carriage 112 and is movable horizontally as the arm 117 rocks against the periphery of the segments of one 'or the other of the grinders 2. The movement of the supports 114 and ofthe arm 11.7 is efmovement. relatively thereto, and coacting fectedby'means of a screw 119 journaled in the carriage 112 and held from endwise with a block 120 which is connected by links 121 to the T supports 114 between the upper and lower ends of the supports 114, the links being connected to the block and to the legs of the T supports by ball-and-socket joints 122, 123. The block 120 is connected to the rock arm 117 to actuate the same by means of an arm'124 extending laterally from the block 120, and connected to the arm 125 extending laterally from the lower end of the shaft 118, by a pin-and-slot connection 127. The screw 119 is provided with a hand wheel 129.

Obviously, as the frame 106 is swung into operative position and the screw- 11.0 operated by the hand wheel 111 to properly position the carriage 108, the cutters 113 and 116 will be moved into engagement with the abrading segments 5 of thegrinders 2, and

as the hand wheel 129 is turned, the cutters or trimmers 113 will be moved back and forth-over the outer side faces'of the segments as the grinders 2 rotate, and at the same time, the tool 116 will be moved laterv ally across the peripheries of the abrading segments.

An individual carriage 112 with its outters is provided for each pressure angle and the trimmers or cutters thereof are properly set to cut the faces of the segments to the predetermined. pressure angles at right angles'to the axes of the respective grind erspreviously adjusted, this carriage 112 being detachably secured to the carriage 108 by screws 132, Fig. 15, which extend through openings 133 into the base of thecarriage 112'and thread into the carriage 108. Suitable gages 134 are provided for determining the amount of movement inwardly of the carriage 108 by the screw 110, there being a gage or distance piece provided for each size of the :gear, and the gage or distance piece is inserted between a color or shoulder 135 on the carriage, Fig. 17, and the opposing face of the frame 106.

he cutters or points 113, 116 are-suitably clamped in split bearings 130 providedin each support 114 and in =the arm 117, these split bearings beingclamped by screws 131.

In the operation of the machine, after the grinders have been trimmed a gear is placed and alined on the spindle 21 as described, and power applied to the grinders 2 and the shaft 50,the carrage 19 is reciprocated rolling the gear so that teeth thereof engage with the grinders 2, this rolling action being due to'the movement of the carriage and to the rotation of the gear effected by the roller 60'and straps 61, 62. At the end of each \a'eciprocation of the carriage, the tail 87 of the lock 84: engages the fixed shoulder 88 moving the lock out of engagement with the rack 83, and thereupon the rod 74 is actuated by the rocking lever 75 and cam 77 to actuate the pawl carrier 73 and hence cause the pawl to shift the ratchet wheel 71 and gear spindle s'upport38 to rotate the gear relatively to the roller 60 to bring new teeth into position to be ground during next reciprocation of the carriage. Owing to the large grinding surface due to the segments 5 on the large disks, the segments do not become heated or rather are not brought into engagement with gears I while heated, as they have ample time to 0001. Furthermore, owing to the large grinders and the casing inclosing the same, air-is circulated and blown on the gear being ground so that it is unnecessary to grind the same in water.

What I claim is 1. A gear grinding machine comprising a pair of grinding wheels opposed to each other and. arranged with their axes inclined with respect to each other so that their working faces are'in the planes of the pressure angles of the teeth; of .the gear to, be v ground and at right angles to the axes of the grinding wheels, and a gear carriage arranged to support the gear with its axis standing at an angle to the plane containing the axes of the grinder so that the teeth thereof are engaged with the grinders and the grinders extend between teeth of the gear and the working faces thereof are en- 5 gaged with dissimilar faces of alternate teeth of the gear, substantially as and for the purpose set forth. 2. A gear grinding machine comprising a plurality of grinders rotatable about fixed axes and arranged with their axes inclined so that portions of their rims run close together, the outer side faces of the grinders at the points they run nearest together beingarranged in the planes of the pressure angles of the teeth of the gear being ground and at right angles to said inclined axes, the

grinders being adjustable to change theinclination of their axes, substantially as and v for the purpose set forth.

3. A gear grinding machine comprising a plurality of grinders rotatable about fixed ,axes, a gear carriage arranged to support the gear with teeth thereof engaged with the grinders, the grinders extend-ing between teeth of the gear, and means for roll- '0 ing the gear while engaged with the grinders, substantially as and for the purpose described.

4. In a gear grinding machine, a frame,.

-. a pair of grinding whels journaled in fixed .5 bearings in the frame and arranged with their axes inclined so'that portions of their rims run close together, the outer side faces of the rims being arranged at a right angle to the axes of the grinders, respectively, a

40 gear carnage arranged to hold a gear with teeth thereof engaged with the outer faces of the rims of the grinders, and means for actuating the gear carriage to roll the geardur ng grinding operation, substantially as 4'5 and for the purpose specified.

' 5. A gear grinding machine comprising a plurality of grinders rotatable about fixed axes, a gear carriage arranged to support the gear with teeth thereof en aged with the grinders and with the grin ers extending between teeth of the gear and engaging dissimilar faces of alternate teeth of the gear,

and means for'rolling'the gear during the grlndlng operation, substantially as and for the purpose set forth.

6. In a gear grinding machine, a frame formed with fixed bearings, grinding wheels having axles journaled in the bearings, the

bearings being arranged inclined relatively to'each other whereby portions of the rims of the wheels converge and' run near" each other, and the bearings being .adjustable to changethe an les of the axes of the grindmg wheels, an aar carriage arranged to is hold a gear with e working faces of teeth thereof engaged with the outer sides of the rims of the gi inding wheels at the point,the wheels run nearest together, substantially as and for the purpose described.

' 7. In a gear grindin machine, a frame formed with fixed earings, grinding wheels having axles journaled in the bearings, the bearings being arranged inclinedrelatively to each other whereby portions of the rims of the wheels converge and run near each other, and the bearings being adjustable to change the angles of theinclinations of the axes of the grinding wheels, the outer side faces of the rims of.the wheels being arranged in planes at right angles to the axes of-the wheels, respective ly, a gear carriage arranged to hold a. gear with the working faces of teeth thereof engaged with the outer sides ofthe rims'of the grinding wheels at the pointthe wheels run nearest together, and means for rolling the gear I during the grinding. operation, substantially as and for the purposespecified.

8. A gear grinding machine comprising a 'plurality of grinders, a gear carriage arranged-to support the gear with teeth thereof engaged with the grinders, the grindersextending between teeth of the gear, means for moving the carriage crosswise of the rims of the, grinders and means for moving the gear about its axis during movement of the carriage, substantiallyas and for the purpose set forth. 9. A gear grinding machine comprising a plurality of grinders, and a gear carriage arranged to support the gear with teeth thereof engaged with ,the' grinders, thd

grinders extending between teeth of the ear the inders bein en a ed respect ively with front and rdiirffce s of difl'erent teeth of the gear, means for moving the carriage. crosswise of the grinders, and means for moving the during said movement 0 the carriage, substantially as and for the purposedescribed. 10. Ina gear grinding machine, a grindear about its axis in wheel a ear carria e arran ed to su .n g vv grinder, a gear support arranged to hold the I gear with a working face thereof engaged .with the grinder, and with the grinder extending between teeth of the gear, means for rolling the gear during the grinding operation, the rolling movement carrying the" gearinto and outof engagement with 

